Thanks! FWIW, my P/J 5 has an ash body and ebony board. This is of course not a "traditional" wood combination, but I figured that the P/J setup was a bit of a deviation from "vintage" already, and I like the extra clarity and "ping" that I get from an ebony board. Combined with my fingerstyle playing mostly over the neck pickup, I find that an ebony board lets me cover a wide range of tones, and even emulate a pick attack to a certain extent. And of course, there's always that VTC if things get to snappy up top.
As for specific ash/rosewood combinations, I think my only current bass with that setup is my Fbass VF5. George specifically recommended that wood combo, citing the strong lows and sweet high end, and that is certainly what my VF5 delivers. I have played several other ash/rosewood J-style basses which I really liked (including a sweet DJ4 that I recently traded away), but I don't think I've played an ash/rosewood P-bass. I definitely agree with you as to ash/maple in a P-bass (my '74 Precision is ash/maple). It's quite a departure from alder/rosewood in a P-bass (which I also like a lot, but I see as something very different). I could see where ash/rosewood would work really well in a P-bass, though. I may have to give it a try one of these days!
Tom.